U.S. patent number 6,855,960 [Application Number 10/354,110] was granted by the patent office on 2005-02-15 for flat panel display with black matrix and method of fabricating thereof.
This patent grant is currently assigned to Samsung SDI Co., Ltd.. Invention is credited to Chang-Su Kim, Hye-Dong Kim, Sang-Il Park, Dong-Chan Shin.
United States Patent |
6,855,960 |
Park , et al. |
February 15, 2005 |
Flat panel display with black matrix and method of fabricating
thereof
Abstract
An organic electroluminescent display in which a black matrix
with a concentration gradient of a transparent material and a
metallic material is formed on the same surface as a pixel
electrode. The black matrix and a pixel electrode of the organic
electroluminescent display are formed using only one masking
operation. The black matrix has a concentration gradient of a
continuous gradient structure in which constituents of the
transparent material are continuously decreased while constituents
of the metallic material are continuously increased as a thickness
of the black matrix is increased, a step gradient structure in
which the constituents of the transparent material are gradually
decreased while the constituents of the metallic material are
gradually increased as the thickness of the black matrix is
increased, or a multi-gradient structure in which the continuous
gradient structure and/or the step gradient structure are
repeated.
Inventors: |
Park; Sang-Il (Seoul,
KR), Shin; Dong-Chan (Hwaseong-gun, KR),
Kim; Hye-Dong (Seongnam, KR), Kim; Chang-Su
(Suwon, KR) |
Assignee: |
Samsung SDI Co., Ltd.
(Suwon-Si, KR)
|
Family
ID: |
28786951 |
Appl.
No.: |
10/354,110 |
Filed: |
January 30, 2003 |
Foreign Application Priority Data
|
|
|
|
|
Apr 15, 2002 [KR] |
|
|
2002-20426 |
|
Current U.S.
Class: |
257/98; 257/191;
257/437 |
Current CPC
Class: |
H01L
51/5284 (20130101); H01L 51/56 (20130101); H01L
27/3244 (20130101); H01L 27/3248 (20130101) |
Current International
Class: |
H01L
27/28 (20060101); H01L 51/50 (20060101); H01L
51/56 (20060101); H01L 27/32 (20060101); H01L
51/52 (20060101); H01L 033/00 () |
Field of
Search: |
;438/29-32,69-72,149-161
;257/185-192,98,431-437 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Everhart; Caridad
Assistant Examiner: Lee; Calvin
Attorney, Agent or Firm: Stein, McEwen & Bui, LLP
Claims
What is claimed is:
1. A flat panel display comprising: a substrate; a pixel electrode
formed on the substrate; a black matrix having a plurality of
layers and formed on the same surface as the pixel electrode; a
first insulating layer formed on a front surface of the substrate;
a thin film transistor formed on the first insulating layer
corresponding to the black matrix so as to be connected to the
pixel electrode; a capacitor formed over the first insulating layer
corresponding to the black matrix so as to be connected to the thin
film transistor; and a second insulating layer formed on the front
surface of the substrate having an opening part which exposes a
part of the pixel electrode.
2. The flat panel display according to claim 1, wherein the black
matrix comprises a patterned layered structure of a pixel electrode
material for the pixel electrode, and a black matrix material
including a transparent material and a metallic material so as to
form a pattern having a concentration gradient.
3. The flat panel display according to claim 2, wherein the pattern
having a concentration gradient for the black matrix has a
concentration gradient of a continuous gradient structure in which
constituents of the transparent material are continuously decreased
while constituents of the metallic material are continuously
increased as a thickness of the black matrix is being increased, a
step gradient structure in which the constituents of the
transparent material are gradually decreased while the constituents
of the metallic material are gradually increased as the thickness
of the black matrix is being increased, or a multi-gradient
structure in which the continuous gradient structure and/or the
step gradient structure are repeated.
4. The flat panel display according to claim 1, wherein the black
matrix is electrically connected to the capacitor so as to be used
as an electrode of the capacitor.
5. The flat panel display according to claim 2, wherein the pixel
electrode and the black matrix are structures which are
simultaneously formed on the same surface by selectively removing
the pixel electrode and black matrix materials.
6. The flat panel display according to claim 2, wherein the pixel
electrode and the black matrix are structures which are formed
using only one masking operation.
7. The flat panel display according to claim 2, wherein the
metallic material includes at least one of Al, Cr, Mo, Ti, Ag, Au,
W, and Cu.
8. The flat panel display according to claim 2, wherein the
transparent material Is a transparent dielectric material.
9. The flat panel display according to claim 8, wherein the
transparent dielectric material is one of SiO.sub.2 and
SiN.sub.x.
10. The flat panel display according to claim 2, wherein the
transparent material is a transparent conductive material.
11. The flat panel display according to claim 10, wherein the
transparent conductive material is one of ITO, IZN, and ZnO.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
This application claims the benefit of Korean Patent Application
No. 2002-20426 filed on Apr. 15, 2002, in the Korean Intellectual
Property Office, the disclosure of which is incorporated herein by
reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a flat panel display, and more
particularly, to an organic electroluminescent display in which a
pixel electrode and a black matrix with a concentration gradient of
a transparent material and a metallic material are formed on the
same surface of a substrate, and a method of fabricating thereof
without an additional masking operation.
2. Description of the Related Art
FIG. 1 illustrates a cross-sectional view of a conventional active
matrix organic electroluminescent display.
Referring to FIG. 1, a thin film transistor (TFT) and a capacitor
are formed on a first region 101 of a dielectric substrate 100, on
an upper part of which a buffer layer 110 is formed. The thin film
transistor is equipped with source/drain regions 125 and 126 which
are formed on a semiconductor layer 120, a gate electrode 131 which
is formed on a gate insulating layer 130, and source/drain
electrodes 151 and 152 which are formed on an interlayer insulating
layer 140 so as to be electrically connected to the source/drain
regions 125 and 126, respectively, through contact holes 141 and
142.
The capacitor is equipped with a first electrode 135 formed on the
gate insulating layer 130 and a second electrode 155 connected to
the source electrode 151. A part interposed between the first and
second electrodes 135 and 155 in the interlayer insulating layer
140 functions as a dielectric layer of the capacitor.
An organic electroluminescent display device is formed on the
second region 102 of the dielectric substrate 100. The organic
electroluminescent display device is equipped with a pixel
electrode 170 which is formed on a passivation layer 160 so as to
be electrically connected to the drain electrode 152 through a via
hole 161, an organic electroluminescent layer 190 which is formed
on the pixel electrode 170 exposed through an opening part 185, and
a metal electrode 195 which is formed on a planarization layer 180
comprising the organic electroluminescent layer 190.
A flat panel display such as an active matrix organic light
emitting device (AMOLED) with the foregoing structure includes a
switching device and various wirings to impress power supply to the
switching device, wherein an external light is reflected by a
metallic material of the wirings.
For example, contrast is greatly deteriorated since the external
light is reflected by a metallic material which is used to form a
gate electrode and a lower electrode of the capacitor, an electrode
material which is used to form source/drain electrodes and an upper
electrode of the capacitor, and an electrode material which is used
to form a cathode.
To prevent the deterioration of contrast due to a reflection of
external light, an expensive polarizer has been adhered to a front
surface of a conventional organic electroluminescent display.
However, in addition to an increase in manufacturing cost due to
the use of the polarizer, transmittancy of the display is
deteriorated. That is, since the polarizer itself blocks light
emitted from an organic electroluminescent layer of the display,
luminance is also decreased.
Furthermore, in a conventional display, a black matrix comprising
Cr/CrO.sub.x or an organic layer is separately formed on a region
where a thin film transistor and a capacitor are formed. However, a
conventional fabrication method thereof is complex and problematic
as the method necessarily requires a separate masking operation to
form the black matrix.
SUMMARY OF THE INVENTION
Accordingly, an aspect of the present invention is to provide a
flat panel display having a pixel electrode and a black matrix in
which the black matrix and the pixel electrode are simultaneously
formed on the same surface, and a fabrication method thereof.
Another aspect of the present invention is to provide a flat panel
display having a black matrix which is capable of preventing a
deterioration of contrast and improves luminance by preventing a
reflection due to external light, and a fabrication method thereof
without an additional masking operation.
Additional aspects and advantages of the invention will be set
forth in part in the description which follows and, in part, will
be obvious from the description, or may be learned by practice of
the invention.
To achieve the above and/or other aspects of the present invention,
there is provided a method of fabricating a flat panel display, the
method comprising sequentially forming a pixel electrode material
and a black matrix material on a dielectric substrate,
simultaneously forming a pixel electrode and a black matrix on the
substrate by patterning the pixel electrode material and the black
matrix material, forming a first insulating layer on a front
surface of the substrate, forming a thin film transistor connected
to the pixel electrode and a capacitor connected to the thin film
transistor on the first insulating layer corresponding to the black
matrix, forming a second insulating layer on the front surface of
the substrate, and forming an opening part exposing a part of the
pixel electrode by etching the first and second layers.
The black matrix material may comprise a transparent dielectric
material such as SiO.sub.2 and SiN.sub.x and a metallic material,
or a transparent conductive material such as ITO, IZO, and ZnO and
a metallic material. The black matrix material may have a
concentration gradient of a continuous gradient structure in which
constituents of the transparent material are continuously decreased
while constituents of the metallic material are continuously
increased as a thickness of the black matrix is being increased, a
step gradient structure in which the constituents of the
transparent material are gradually decreased while the constituents
of the metallic material are gradually increased as the thickness
of the black matrix is being increased, or a multi-gradient
structure in which the continuous gradient structure and/or the
step gradient are repeated.
To achieve the above and/or other aspects of the present invention,
there is provided a flat panel display comprising a dielectric
substrate, a pixel electrode formed on the dielectric substrate, a
black matrix formed on the same surface as the pixel electrode, a
first insulating layer formed on a front surface of the dielectric
substrate, a thin film transistor formed on the first insulating
layer corresponding to the black matrix so as to be connected to
the pixel electrode, a capacitor formed on the first insulating
layer corresponding to the black matrix so as to be connected to
the thin film transistor, and a second insulating layer formed on
the front surface of the dielectric substrate having an opening
part which exposes a part of the pixel electrode.
BRIEF DESCRIPTION OF THE DRAWINGS
These and other objects and advantages of the present invention
will become apparent and more readily appreciated from the
following description of the embodiments, taken in conjunction with
the accompanying drawings of which:
FIG. 1 is a cross-sectional view of a conventional organic
electroluminescent display;
FIG. 2A to FIG. 2E are cross-sectional views illustrating a method
of fabricating an organic electroluminescent display according to
an embodiment of the present invention;
FIG. 3 is a cross-sectional view illustrating a method of
fabricating an organic electroluminescent display according to
another embodiment of the present invention; and
FIG. 4A to FIG. 4B are cross-sectional views illustrating a
concentration gradient of a black matrix material in an organic
electroluminescent display according to the present invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
Reference will now be made in detail to the embodiments of the
present invention, examples of which are illustrated in the
accompanying drawings, wherein like reference numerals refer to the
like elements throughout. The embodiments are described below in
order to explain the present invention by referring to the
figures.
FIG. 2A to FIG. 2E show cross-sectional views illustrating a method
of fabricating an organic electroluminescent display according to
an embodiment of the present invention.
Referring to FIG. 2A, a transparent conductive layer 210 for a
pixel electrode and a layer having a concentration gradient for a
black matrix are sequentially deposited on a transparent dielectric
substrate 200, equipped with a first region 201 on which a thin
film transistor and a capacitor are to be formed and a second
region 202 on which an organic electroluminescent display device is
to be formed. A photosensitive layer 230 is coated on the layer
having a concentration gradient for the black matrix.
Subsequently, parts on which the black matrix and the pixel
electrode are to be formed are defined using a halftone mask 300,
wherein the halftone mask 300 is equipped with a blocking region
310 which completely blocks light to limit a part on which the
black matrix is to be formed, and a semi-transmission region 320
which transmits only a part of the light to limit a part on which
the pixel electrode is to be formed. The residual part except for
the blocking region 310 and the semi-transmission region 320 is a
transmission region which transmits all of the light.
Referring to FIG. 2B, photosensitive layer patterns 231 and 232 are
formed on the first region 201 and the second region 202,
respectively, where the photosensitive layer 230 is patterned using
the halftone mask 300. The photosensitive layer pattern 231 formed
on the first region 201 is formed to correspond to the blocking
region 310 of the halftone mask 300 while the photosensitive layer
pattern 232 formed on the second region 202 is formed to correspond
to the semi-transmission region 320 of the halftone mask 300.
Therefore, the photosensitive layer pattern 232 formed on the
second region 202 has a relatively thinner thickness compared to
the photosensitive layer pattern 231 formed on the first region
201.
Referring to FIG. 2C, the black matrix 225 is formed on the first
region 201 and the pixel electrode 212 is formed on the second
region 202, at the same time, by masking the photosensitive layer
patterns 231 and 232 having a different thickness, and etching the
layer 220 having a concentration gradient and the transparent
conductive layer 210. The black matrix 225 includes a transparent
conductive pattern 211 and a pattern 221 having a concentration
gradient. The black matrix 225 is formed on the first region 201
while the pixel electrode 212 having a transparent conductive
pattern is formed on the second region 202 by a thickness
difference between the photosensitive layer patterns 231 and
232.
The layer 220 having a concentration gradient for the black matrix
225 comprises a first component of transparent material and a
second component of metallic material, and has a concentration
gradient of a continuous gradient structure, a step gradient
structure, or a multi-gradient structure.
FIG. 4A and FIG. 4B illustrate cross-sectional views of
concentration gradients of layers for the black matrix 225
according to the present invention. As illustrated in FIG. 4A, with
reference to FIG. 2A to FIG. 2D, the layer 220 for the black matrix
225 has a concentration gradient of a continuous gradient structure
in which a first component of transparent material is gradually
decreased while a second component of metallic material is
gradually increased as a thickness of the black matrix 225 is being
increased from a surface of the substrate 200, that is, as a
distance of external incidence light is becoming more distant.
On the other hand, as illustrated in FIG. 4B, with reference to
FIG. 2A to FIG. 2D, the layer 220 for the black matrix 225 has a
concentration gradient of a step gradient structure in which a
first component of transparent material is decreased in steps while
a second component of metallic material is increased in steps as a
thickness of the black matrix 225 is being increased from the
surface of the substrate 200, that is, as a distance of external
incidence light is becoming more distant. The layer 220 for the
black matrix 225 may have a step gradient structure in which the
first and second components are decreased and increased in five
steps.
Although not shown, the layer 220 for the black matrix 225 can have
a concentration gradient of a multi-gradient structure in which the
continuous gradient of FIG. 4A is repeatedly formed, a
multi-gradient structure in which the step gradient of FIG. 4B is
repeatedly formed, or a multi-gradient structure in which the
continuous gradient and the step gradient are repeatedly
formed.
A transparent dielectric material such as SiO.sub.2 and SiN.sub.x,
or a transparent conductive material such as ITO, IZO and ZnO can
be used as the first component of transparent material of the black
matrix 225, and Al, Cr, Mo, Ti, Ag, Au, W, and Cu can be used as
the second component(s) of metallic material of the black matrix
225.
In one aspect of the present invention, the pixel electrode
material 210 and the layer 220 having a concentration gradient can
be deposited in in-situ, in an operation of FIG. 2A, where a
material having concentration gradients of a transparent conductive
material and a metallic material for a pixel electrode is used as
the layer 220 having a concentration gradient for the black matrix
225.
A black matrix having the foregoing structure prevents a reflection
of external light since a light absorption ratio is increased as a
thickness of the black matrix is increased from a surface of a
substrate, that is, as a distance of external incidence light is
more distant.
As described above, a fabrication method of the organic
electroluminescent display can be simplified since a separate
masking operation to form the black matrix 225 is excluded where
the black matrix 225 including the transparent conductive pattern
211 and the pattern 221 having a concentration gradient, and the
pixel electrode 212 having a transparent conductive pattern are
simultaneously formed on the substrate 200 using the halftone mask
300.
Referring to FIG. 2D and FIG. 2E, a thin film transistor, a
capacitor and an organic electroluminescent display device are
formed after the forming of the black matrix 225 and the pixel
electrode 212. A buffer layer 240 is first formed on a front
surface of the substrate 200 on which the black matrix 225 and the
pixel electrode 212 are formed, and a semiconductor layer 250 is
formed on the buffer layer 240 of the first region 201.
Subsequently, a gate insulating layer 260 is formed on the buffer
layer 240 having the semiconductor layer 250, and a gate electrode
261 and a first electrode 265 of the capacitor are simultaneously
formed on the gate insulating layer 260 of an upper part of the
semiconductor layer 250. Source/drain regions 255 and 256 are
formed, for example, by ion implanting certain conductive type
impurities, for example, n type or p type impurities into the
semiconductor layer 250 after the forming of the gate electrode 261
and the first electrode 265 of the capacitor.
Thereafter, as shown in FIG. 2E, contact holes 271, 272 and 273
which expose the source/drain regions 255 and 256, and the pixel
electrode 212, are formed by forming an interlayer insulating layer
270 on the front surface of the substrate 200, and etching the
interlayer insulating layer 270, the gate insulating layer 260 and
the buffer layer 240.
A source electrode 281, which is electrically contacted with one of
the source/drain regions, for example, a source region 255 through
the contact hole 271, and a second electrode 285 of the capacitor,
which is connected to the source electrode 281, are formed by
patterning a metallic material after depositing the metallic
material on the interlayer insulating layer 270 having the contact
holes 271, 272 and 273. Furthermore, a drain electrode 282, which
is electrically contacted with the drain region 256 through the
contact hole 272 and electrically connected to the pixel electrode
212 through the contact hole 273, is formed.
An opening part 295 is formed by etching a passivation layer 290,
the interlayer insulating layer 270, the gate insulating layer 260,
and the buffer layer 240 so as to expose the pixel electrode 212
after the forming of the passivation layer 290 on the front surface
of the substrate 200. Although not shown, a cathode is formed after
forming an organic electroluminescent layer on the pixel electrode
212 in the opening part 295.
FIG. 3 illustrates a cross-sectional view of an organic
electroluminescent display, which is a flat panel display,
according to another embodiment of the present invention. In this
embodiment, a black matrix 325 is used as an electrode of a
capacitor, and the black matrix 325 includes a transparent
conductive pattern 311 and a pattern 321 having a concentration
gradient. A pixel electrode 312 having a transparent conductive
pattern and the black matrix 325 are formed on the same surface of
a substrate 300, as in the embodiment shown in FIG. 2A to FIG.
2F.
That is, in this embodiment, a capacitor having a parallel
structure along with a second electrode 365 and a third electrode
385 is formed by using the black matrix 325 as a first electrode of
the capacitor.
A method of forming the black matrix 325, which includes the
transparent conductive pattern 311 and the pattern 321 having a
concentration gradient, and the pixel electrode 312 having a
transparent conductive pattern on the dielectric substrate 300 is
the same as that of the embodiment of FIG. 2A to FIG. 2E.
Thereafter, an interlayer insulating layer 370 is formed on a front
surface of the substrate 300 after forming a semiconductor layer
350 equipped with source/drain regions 355 and 356 on a buffer
layer 340, and forming a gate 361 and a second electrode 365 of the
capacitor on a gate insulating layer 360.
Subsequently, the interlayer insulating layer 370 is etched to form
first and second contact holes 371 and 372 which expose the
source/drain regions 355 and 356, a third contact hole 373 which
exposes the pixel electrode 312, and a fourth contact hole 374
which exposes the pattern 321 having a concentration gradient of
the black matrix 325, at the same time.
A conductive material for source/drain electrodes 381 and 382 is
deposited and patterned on the interlayer insulating layer 370 to
form, for example, the source electrode 381, which is contacted
with the source region 355 through the first contact hole 371, the
drain electrode 382 which is simultaneously contacted with the
drain region 356 through the second contact hole 372 and contacted
with the pixel electrode 312 through the third contact hole 373,
and a third electrode 385 of the capacitor which is simultaneously
connected to the source electrode 381 and connected to the black
matrix 325 through the fourth contact hole 374.
The black matrix 325 is conductive and used as a first electrode of
the capacitor. Accordingly, a transparent conductive material such
as ITO, IZO and ZnO can be used as a first component of the black
matrix 325 while a metallic material such as Al, Cr, Mo, Ti, Ag,
Au, W and Cu can be used as a second component of the black matrix
325.
According to the foregoing embodiments of the present invention, a
separate masking operation to form a black matrix can be omitted
since the black matrix and a pixel electrode can be simultaneously
formed on the same surface of a substrate using a halftone mask
using only one cycle of a masking operation. Additionally, a
conventional insulating layer deposition operation to insulate the
pixel electrode from source/drain electrodes can be omitted in the
present invention. Also, a separate masking operation to form a via
hole which connects the pixel electrode and the source/drain
electrodes can be omitted in the present invention. Therefore, the
foregoing embodiments of the present invention result in process
simplification and yield improvement.
Furthermore, in a flat panel display having a black matrix and a
fabrication method thereof according to the foregoing embodiments
of the present invention, a luminance can be improved by preventing
a reflection due to external light without using an expensive
polarizer, thereby improving a transmittancy.
Although a few embodiments of the present invention have been shown
and described, it will be appreciated by those skilled in the art
that changes may be made in these embodiments without departing
from the principles and spirit of the invention, the scope of which
is defined in the appended claims and their equivalents.
* * * * *